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Purpose: Soil erosion and sediment transport are often induced by a few extreme precipitation events. Currently, there is limited information on the effects of changes in precipitation extremes on river sediment load over a long time period at the basin scale. The objectives of this study were to quantify the effects of variations in precipitation extremes on sediment load in the Second Songhua River Basin (SSRB), northeast China. Materials and methods: Daily precipitation data from 10 meteorological stations within the SSRB and sediment load data during 1960–2014 from the basin outlet hydrological station were collected. Six extreme precipitation indices, such as erosive precipitation (ERPTOT), wet-day precipitation (PRCPTOT), very wet day precipitation (R95pTOT), flood season precipitation (FSPTOT), maximum 1-day precipitation (RX1day) and heavy precipitation (HP), were used to detect the precipitation extremes. The Mann–Kendall non-parametric trend analysis was used to analyze the dynamic changes in precipitation extremes and sediment load. The double cumulative curve method was used to assess the effects of changes in precipitation extremes on sediment load. Results and discussion: The results indicated that six extreme precipitation indices showed periodic variations from 1960 to 2014, while they did not show any significant change trend in the SSRB (p > 0.05); however, the sediment load showed an extremely significant decreasing trend (p < 0.01) over the past 55 years. Sediment load significantly correlated with six precipitation extremes indices (p < 0.05). Compared with the baseline period (1960–1977), the sediment load was reduced by 1.12 × 106 ton per year (1977–2014). The contribution of precipitation extremes to the sediment load ranged from -22.83% to 6.97%. The corresponding contribution of the non-precipitation factor to sediment load was from 93.03% to 122.83%. Conclusions: The change in precipitation extremes was not the main reason for the sediment load reduction. Sediment load reduction in the SSRB was due to the interactions between multiple factors. Non-precipitation factors, such as reservoir construction, were the main reasons for the sediment load reduction. These findings are useful to understand the variation of river sediment load and to adopt countermeasures to relieve potential risk of precipitation extremes. [ABSTRACT FROM AUTHOR]

River‐dominated marginal seas are important carbon sinks on Earth. However, their carbon sequestration capacities are changing due to increased anthropogenic perturbations. Herein, we employ substantial datasets to study the characteristics of organic carbon (OC) from the East China Sea (ECS) in 2006 and 2018 and reveal the impacts of reservoir construction on the OC deposition in this region. We show that the distribution of sedimentary OC in the ECS is primarily controlled by riverine input and seabed erosion processes. Hydrodynamic processes influence the OC deposition due to both the scouring of fine‐grained sediments and selective degradation of OC associated with the sediment mobilization. The deposition flux of OC in the ECS decreased by 48% after reservoir construction. These findings demonstrate that reservoir construction seriously affected the OC deposition in the ECS and may be applicable to river‐dominated continental shelves worldwide. Key Points: Reservoir construction changed the transport process and deposition pattern of organic carbon in the East China SeaThe deposition flux of organic carbon in the East China Sea decreased by 48% due to reservoir constructionDeposition flux reduction threatens river‐dominated margins worldwide and should be taken seriously [ABSTRACT FROM AUTHOR]

Purpose: The Mississippi River is the largest river in the USA and one of the most regulated rivers in the world. Understanding fluvial sediment flux changes in the Mississippi River system has critical implications for future sustainable development and management strategies. Materials and methods: We obtained annual runoff and suspended sediment series from the United States Geological Survey (USGS) Data Series. Here, we investigated temporal trends and historical phases of fluvial sediment flux, while also quantifying the driving forces of changes in sediment loads in the Mississippi River system using a sediment identity approach and the sediment survey records. Results and discussion: Since the earliest estimates (initially 400–500 Mt year−1), land-ocean sediment reduction in the Mississippi River system has displayed two temporal phases, decreasing from 350 Mt year−1 during 1952–1962 to 200 Mt year−1 during 1963–2009. The decline in land-ocean sediment flux was the result of an increase in precipitation and water yield capacity being outweighed by a decrease in sediment concentration. It is estimated that a total of 24 Gt of sediment was trapped by dams and reservoirs from 1985 to 2015, while the amount of sediment reduction by soil conservation is estimated to be 15 Gt in the USA. We can deduce that reservoir construction was the dominant driver (~ 62%) influencing land-ocean sediment flux from the Mississippi River system during 1985–2015. During 1950s–1960s, reservoirs played an overwhelmingly primary role in reducing riverine sediments. In the Missouri River basin, the largest contributor of sediment to the lower Mississippi River, we found a dominant role (> 53%) of reservoirs on tributaries in trapping sediments. The decrease in land-ocean sediment flux has caused degradation of the Mississippi River delta. Conclusions: Human activities are the main factors influencing changes in land-ocean sediment flux. Therefore, there is an urgent need of a basin-wide strategic plan to maximize the benefits and minimize the risks in order to achieve sustainable management of the drainage basin and river delta. [ABSTRACT FROM AUTHOR]

Irrigation plays a significant role in achieving food and nutrition security in dry regions. However, detailed ex-ante appraisals of irrigation development investments are required to efficiently allocate resources and optimize returns on investment. Due to the inherent system complexity and uncertain consequences of irrigation development interventions coupled with limited data availability, deterministic cost-benefit analysis can be ineffective in guiding formal decision-making. Stochastic Impact Evaluation (SIE) helps to overcome the challenges of evaluating investments in such contexts. In this paper, we applied SIE to assess the viability of an irrigation dam construction project in northern Ethiopia. We used expert knowledge elicitation to generate a causal model of the planned intervention's impact pathway, including all identified benefits, costs and risks. Estimates of the input variables were collected from ten subject matter experts. We then applied the SIE tools: Monte Carlo simulation, Partial Least Squares regression, and Value of Information analysis to project prospective impacts of the project and identify critical knowledge gaps. Model results indicate that the proposed irrigation dam project is highly likely to increase the overall benefits and improve food and nutrition status of local farmers. However, the overall value of these benefits is unlikely to exceed the sum of the investment costs and negative externalities involved in the intervention. Simulation results suggest that the planned irrigation dam may improve income, as well as food and nutrition security, but would generate negative environmental effects and high investment costs. The Stochastic Impact Evaluation approach proved effective in this study and is likely to have potential for evaluating other agricultural development interventions that face system complexity, data scarcity and uncertainty. Unlabelled Image • Probabilistic decision model is applied to assess an irrigation development project. • Expert knowledge elicitation is used to generate an impact pathway model of the decision. • The project is expected to improve income and nutritional status of local farmers. • The project requires high investment and negatively affects the environment. • The overall cost of the project probably exceeds the sum of all expected benefits. [ABSTRACT FROM AUTHOR]

• The meteorological Lepage test effectively anlyzed the temporal variation of the water and sediment discharge for the first time. • The increase in sediment transport within tributaries and during short-term flood events has become a key characteristic of the upper Yangtze River in recent years. • The reduction in sediment entering the Three Gorges Reservoir decreased its downstream sediment reduction effect. After the construction of the cascade reservoirs in the lower Jinsha River, it has become necessary to clarify the spatial and temporal variability of the volume of sediment entering the Three Gorges Reservoir in order to manage sediment within the basin considering the new situation of rapid sediment reduction. Previous studies were affected by the inaccurate analyses of transition points and associated causes and were unable to identify clear changes in the spatial and temporal characteristics. Therefore, the impact that the Three Gorges Reservoir has on sediment reduction in the upper Yangtze River needs to be reassessed. The Lepage test and sediment identity factor method were applied to reveal that the sediment transported by the Jinsha River has significantly decreased since 2013 due to the reservoir construction, while the sediment transported by the Min River and Jialing River has slightly increased since 2014 and 2015 due to heavy rainfall. However, this has ultimately led to a significant reduction in sediment entering the Three Gorges Reservoir since 2013. Accordingly, the spatial composition of sediment sources in the Three Gorges region has been dominated by tributaries in recent years, with the Jialing River accounting for 38.98 % of the total and the Jinsha River accounting for only 1.74 %. Under these new conditions, sediment transported during short-term floods becomes more important, with sediment entering the Three Gorges Reservoir during 7 day flood events accounting for up to 47.16 % of the total transport in a year. As a result of sediment trapping by the upstream reservoirs, the Three Gorges Reservoir is responsible for only 7.5 % to 22.75 % of the sediment reduction observed at Yichang Station. Understanding the weakened impact that the Three Gorges Reservoir has on the sediment reduction phenomenon in the upper Yangtze River is important for managing the schedules of the reservoirs in the upper Yangtze River. [ABSTRACT FROM AUTHOR]

Understanding vegetation dynamics is necessary to address potential ecological threats and develop sustainable ecosystem management at high altitudes. In this study, we revealed the spatiotemporal characteristics of vegetation growth in the Lhasa River Basin using net primary productivity (NPP) and normalized difference vegetation index (NDVI) during the period of 2000–2005. The roles of climatic factors and specific anthropogenic activities in vegetation dynamics were also identified, including positive or negative effects and the degree of impact. The results indicated that the interannual series of NPP and NDVI in the whole basin both had a continuous increasing trend from 102 to 128 gC m−2 yr−1 and from 0.417 to 0.489 (p < 0.05), respectively. The strongest advanced trends (>2 gC m−2 yr−1 or >0.005 yr−1) were detected in mainly the southeastern and northeastern regions. Vegetation dynamics were not detected in 10% of the basin. Only 20% of vegetation dynamics were driven by climatic conditions, and precipitation was the controlling climatic factor determining vegetation growth. Accordingly, anthropogenic activities made a great difference in vegetation coverage, accounting for about 70%. The construction of urbanization and reservoir led to vegetation degradation, but the farmland practices contributed the vegetation growth. Reservoir construction had an adverse impact on vegetation within 6 km of the river, and the direct damage to vegetation was within 1 km. The impacts of urbanization were more serious than that of reservoir construction. Urban sprawl had an adverse impact on vegetation within a 6 km distance from the surrounding river and resulted in the degradation of vegetation, especially within a 3 km range. Intensive fertilization and guaranteed irrigation improved the cropland ecosystem conditions, creating a favorable effect on the accumulation of crop organic matter in a range of 5 km, with an NPP trend value of 1.2 gC m−2 yr−1. The highly intensive grazing activity forced ecological environmental pressures such that the correlation between livestock numbers and vegetation growth trend was significantly linear negative.

Regular sediment inputs are required for deltas to maintain their surface elevation relative to sea level, which is important for avoiding salinization, erosion, and flooding. However, fluvial sediment inputs to deltas are being threatened by changes in upstream catchments due to climate and land use change and, particularly, reservoir construction. In this research, the global hydrogeomorphic model WBMsed is used to project and contrast ‘pristine’ (no anthropogenic impacts) and ‘recent’ historical fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas. Additionally, 12 potential future scenarios of environmental change comprising combinations of four climate and three socioeconomic pathways, combined with a single construction timeline for future reservoirs, were simulated and analysed. The simulations of the Ganges-Brahmaputra-Meghna delta showed a large decrease in sediment flux over time, regardless of future scenario, from 669 Mt/a in a ‘pristine’ world, through 566 Mt/a in the ‘recent’ past, to 79–92 Mt/a by the end of the 21st century across the scenarios (total average decline of 88%). In contrast, for the Mahanadi delta the simulated sediment delivery increased between the ‘pristine’ and ‘recent’ past from 23 Mt/a to 40 Mt/a (+77%), and then decreased to 7–25 Mt/a by the end of the 21st century. The Volta delta shows a large decrease in sediment delivery historically, from 8 to 0.3 Mt/a (96%) between the ‘pristine’ and ‘recent’ past, however over the 21st century the sediment flux changes little and is predicted to vary between 0.2 and 0.4 Mt/a dependent on scenario. For the Volta delta, catchment management short of removing or re-engineering the Volta dam would have little effect, however without careful management of the upstream catchments these deltas may be unable to maintain their current elevation relative to sea level, suggesting increasing salinization, erosion, flood hazards, and adaptation demands. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms behind land–ocean sediment transport processes is crucial, due to the resulting impacts on the sustainable management of water and soil resources. This study investigated temporal trends and historical phases of sediment flux delivered to the sea by nine major rivers in China, while also quantifying the contribution of key anthropogenic and natural driving forces. During the past six decades, sediment flux from these nine major rivers exhibited a statistically significant negative trend, decreasing from 1.92 Gt yr −1 during 1954–1968 to 1.39 Gt yr −1 , 0.861 Gt yr −1 and 0.335 Gt yr −1 during 1969–1985, 1986–1999 and 2000–2016, respectively. We used a recently developed Sediment Identity approach and found that the sharp decrease in sediment load observed across China was mainly (~95%) caused by a reduction in sediment concentration. Reservoir construction exerted the strongest influence on land–ocean sediment fluxes, while soil conservation measures represented a secondary driver. Before 1999, soil erosion was not controlled effectively in China and reservoirs, especially large ones, played a dominant role in reducing riverine sediments. After 1999, soil erosion has gradually been brought under control across China, so that conservation measures directly accounted for ~40% of the observed decrease in riverine sediments. With intensifying human activities, it is predicted that the total sediment flux delivered to the sea by the nine major rivers will continue to decrease in the coming decades, although at a slower rate, resulting in severe challenges for the sustainable management of drainage basins and river deltas. [ABSTRACT FROM AUTHOR]

The nonparametric Mann-Kendall test and the Pettitt test were employed to examine the change trends and shifts of runoff and sediment input to Poyang Lake between 1961 and 2013. Water balance and linear regression models were used to evaluate the impacts of climate variability and human activities on the runoff and sediment discharge changes. The results showed that runoff inputs to the lake had insignificant temporal trends and change points, while sediment inputs had significant decreasing trends, with an abrupt change in 1989. Quantitative assessment demonstrated that human activities led to a small decrease (5.5%) in runoff inputs to the lake, and a dramatic (121.4%) decrease in sediment inputs to the lake between the reference period (before the change point) and the human-influenced period (after the change point). This work provides a useful reference for future policy makers in water resource utilization and environmental safety of the Poyang Lake basin. [ABSTRACT FROM PUBLISHER]

In-depth studies of water and sediment fluxes from rivers into the sea are very important for understanding the interactions between land and sea. This paper is concerned with identifying the changes in the time series of water and sediment fluxes from Feiyun River in Zhejiang Province, China. Inter- and intraannual variability in the water discharge and sediment load of the Feiyun River into the sea are analyzed using the observed data of runoff (1956-2008) and sediment (1957-2008) at Xuekou Station, which is in the main channel. The results show that there is a good peak-valley correlation between the water discharge and sediment load, and there are obvious seasonal variations, with a 65.7% water discharge and 89.2% sediment load during the flooding periods. Water discharge is mainly controlled by natural rainfall, but the construction of the upstream reservoirs in 1997 increased the discharge amount in the dry season and decreased the amount in the flooding season. Sediment loads were reduced after a huge flood in 1990 and construction of upstream reservoirs, while the latter also decreased the sediment load during the typhoon flooding period. Furthermore, the correlation between water discharge and sediment load is also affected by the flood and reservoir construction. There are some differences in the regression equations of sediment load and water discharge for 1957-1989, 1991-1996, and 1997-2008. [ABSTRACT FROM AUTHOR]

Southeast Asia (SE Asia) is a known global hotspot of biodiversity and endemism, yet the region is also one of the most biotically threatened. Ecosystems across the region are threatened by an array of drivers, each of which increases the probability of extinction of species in a variety of ecosystems. These issues are symptomatic of the issues that face the global tropics; however, with around 4 billion people in the wider region and the associated pressures on biodiversity, this region may be under some of the greatest levels of biotic threat. Deforestation rates in SE Asia are some of the highest globally, additionally it has the highest rate of mining in the tropics, around the greatest number of hydropower dams under construction, and a consumption of species for traditional medicines which is a threat to biodiversity globally. In this review, the greatest threats to regional biodiversity in the SE Asian region are discussed. Tree-plantations and deforestation represent one of the most imminent threats, and some countries have already lost over half their original forest cover (i.e., the Philippines, parts of Indonesia), with projections of as much as 98% loss for some regions in the coming decade. Hunting and trade represent a significant threat as demand stems not only for food, but also for medicine, for ornamentation, and as a status symbol. Mining represents a frequently overlooked threat, as the Asian region is one of the greatest exporters of limestone and various minerals globally, and the cost of this to biodiversity is not only through the direct loss of areas for mines, but also through the development of roads that further fragment the landscape, the leakage of heavy metals, and the destruction of limestone karsts, which represent global endemicity hotspots. Reservoir construction, wetland drainage, fires, pollution, invasive species, disease, and finally climate change are also considered. Once each issue has been discussed, the overall prognosis of regional biodiversity and priority actions to protect SE Asian biodiversity in the future is discussed. [ABSTRACT FROM AUTHOR]

Over the past decade, intensive human activity, particularly dam construction, has resulted in altered runoff in the Sanchahe River region. In this study, the changes in runoff and flood regime were analyzed using Mann–Kendall trend analysis and linear regression analysis. The annual runoff coefficient (ARC) was selected as the primary index to verify the relationship between reservoirs and change in annual runoff at the outlets of upstream Sanchahe River Basin (Yangchang hydrologic station) and the entire basin (Yachihe hydrologic station). The results indicate that the construction of dams and the subsequent development of reservoirs have significantly influenced stream flow process in the Sanchahe River Basin. As reservoirs in the upstream part of the basin are small in both number and storage capacity, the annual runoff depth decreased only slightly from 1963 to 2012, and this trend was not significant at the 95% confidence level. Trend analyses on ARCs demonstrate that the consumption of water during reservoir construction is likely the cause of decreased runoff depth. In contrast, the annual runoff depth of the entire basin decreased significantly (∼4.01 mm/y). The basin-wide flood regime has been influenced by reservoir construction in the entire Sanchahe River Basin. The annual maximum peak flow (AMPF), annual maximum 3-day flood volume (AM3FV), and annual maximum 7-day flood volume (AM7FV) all decreased significantly at Yachihe station, especially after the construction of the Puding and Yinzidu Reservoir dams. Large floods seldom occurred after the 1990s, and since 2000, no flood cases with a recurrence period of more than 10 years have occurred at the basin outlet. [ABSTRACT FROM AUTHOR]

ABSTRACT The influence of a reservoir on downstream hydrological regime and channel adjustment depends on the operational mode of the reservoir. The Liujiaxia and Longyangxia Reservoirs were completed in 1968 and 1985, respectively, both above Lanzhou. The former controls most suspended sediment supply from the drainage area above Lanzhou station, and the latter controls most runoff generated from the same area; the former has relatively small storage capacity and is used for interseasonal regulation of river flow, and the latter has much larger storage capacity and is used for multiannual regulation of river flow. Thus, the former changes sediment regime greatly, whereas the latter changes flow regime significantly. Of the runoff of the upper Yellow River, more than 95% comes from the drainage area above Lanzhou and less than 5% from below Lanzhou; of the sediment supply, 46% comes from the drainage area above Lanzhou and 56% from below Lanzhou, which cannot be regulated by the two reservoirs. Influenced by these factors, channel fill-scour behaviour after the reservoir construction exhibited a complex response, which can be separated as two stages. The response at the first stage was dominated by the Liujiaxia Reservoir and at the second by the Longyangxia Reservoir. The first stage of response can be generalized as follows: completion of the Liujiaxia Reservoir → large quantity of sediment trapped → downstream channel scour → sediment trapping attenuating due to the decrease of storage capacity → channel scour declining. The second stage of response can be generalized as follows: completion of the Longyangxia Reservoir → significant reduction of high-flow season flow → downstream river flow incapable of carrying sediment supplied below the dam → downstream channel sedimentation enhanced. The changes induced by the two reservoirs occurred successively, and a cycle of complex response occurred during the river channel adjustment. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The creation of large freshwater reservoirs is one of the most dramatic anthropogenic impacts on the natural environment. With worldwide rising demand for water, the construction of more reservoirs is inevitable. Although the effects of reservoir construction on many medically important parasites are well known and appreciated, changes to aquatic wildlife host–parasite interactions have been largely undervalued even though a large body of literature exists. The present review examines changes in the wildlife parasite fauna during the impoundment of reservoirs, focusing on the parasites of invertebrates, fish, and birds, the effects both upstream and downstream of the reservoir, parasitic zoonoses, the associated pollution generated, and assesses the impact of the recently completed Three Gorges Dam in China on the Yangtze River’s parasite fauna. [ABSTRACT FROM AUTHOR]

A vertical (laterally integrated) two-dimensional numerical model was implemented to study the hydrodynamics, saltwater intrusion, and suspended sediment in the Danshuei River–Tahan Stream due to the Shihmen Reservoir construction in the upriver reaches. The construction of the reservoir and water diversion in the upper reaches of the river system significantly reduces the freshwater inflow and drastically changes the river bathymetry. The model was calibrated and verified with the available hydrographic data measured in 1977, 1978, and 1999 as well as measured salinity and suspended sediment concentration in 1999. The overall performance of the model is in reasonable agreement with the field data. The validated model was then used to investigate the change in hydrodynamics, saltwater intrusion, suspended sediment distribution, and flushing time as a result of reservoir construction in upper river of Tahan Stream. The model simulations indicate that more tidal energy propagates into the estuarine system after reservoir construction because of the substantial increase in river cross-sections. The limits of saltwater intrusion after reservoir construction extended farther inland 2–3km than those after reservoir construction. The modelling results also reveal that the suspended sediment concentration before reservoir construction was higher than that after reservoir construction along the river mouth to Kuan-Du due to the significant bathymetric change after the reservoir construction. The calculated estuary flushing time was strongly dependent on river flow and reduced 2.3–25h under different river discharges after reservoir construction due to the change in river bathymetry. [Copyright &y& Elsevier]

Understanding vegetation dynamics is necessary to address potential ecological threats and develop sustainable ecosystem management at high altitudes. In this study, we revealed the spatiotemporal characteristics of vegetation growth in the Lhasa River Basin using net primary productivity (NPP) and normalized difference vegetation index (NDVI) during the period of 2000–2005. The roles of climatic factors and specific anthropogenic activities in vegetation dynamics were also identified, including positive or negative effects and the degree of impact. The results indicated that the interannual series of NPP and NDVI in the whole basin both had a continuous increasing trend from 102 to 128 gC m−2 yr−1 and from 0.417 to 0.489 (p < 0.05), respectively. The strongest advanced trends (>2 gC m−2 yr−1 or >0.005 yr−1) were detected in mainly the southeastern and northeastern regions. Vegetation dynamics were not detected in 10% of the basin. Only 20% of vegetation dynamics were driven by climatic conditions, and precipitation was the controlling climatic factor determining vegetation growth. Accordingly, anthropogenic activities made a great difference in vegetation coverage, accounting for about 70%. The construction of urbanization and reservoir led to vegetation degradation, but the farmland practices contributed the vegetation growth. Reservoir construction had an adverse impact on vegetation within 6 km of the river, and the direct damage to vegetation was within 1 km. The impacts of urbanization were more serious than that of reservoir construction. Urban sprawl had an adverse impact on vegetation within a 6 km distance from the surrounding river and resulted in the degradation of vegetation, especially within a 3 km range. Intensive fertilization and guaranteed irrigation improved the cropland ecosystem conditions, creating a favorable effect on the accumulation of crop organic matter in a range of 5 km, with an NPP trend value of 1.2 gC m−2 yr−1. The highly intensive grazing activity forced ecological environmental pressures such that the correlation between livestock numbers and vegetation growth trend was significantly linear negative. [ABSTRACT FROM AUTHOR]

• The abrupt changes in sediment load were consistent with the operation of reservoir. • Sediment concentration played the dominant role in the reduction of sediment load. • Reservoir construction was highly responsible for the sharp decline in sediment flux. • Driving factors of sediment load variation showed obvious spatial heterogeneity. River sediment flux, the most critical element of land-ocean interaction, is undergoing significant changes due to climate variability and anthropogenic activities. Thus, identifying the driving forces and their contributions to the variation in sediment load is of great significance for sustainable management of soil and water resources. However, the dynamics behind these changes are not well understood, and the quantification of drivers of sediment load change remains scarce. In this study, we investigated the changes in hydrometeorological variables and quantitatively separated drivers of sediment load change in the Yangtze River (YZR) basin, China, during 1956–2015. The Mann-Kendall test and sequential cluster method were employed to examine the trends and abrupt changes in water discharge and sediment load. Results showed that the mean annual precipitation for most sub-basins and water discharge at most stations exhibited no apparent downward trend, while annual temperature showed a significant upward trend for most sub-basins. Sediment load decreased significantly at most stations, with breakpoints occurring around 1968 and in the early 2000s. The whole study period was split into three sub-periods (1956–1968, 1969–2002 and 2003–2015) to quantify the change in sediment load. As indicated by water-sediment relationships at 12 stations, the slope of the double mass curve showed a considerable decreasing trend during the period 2003–2015. A decomposition method based on sediment identity factor analysis was applied to quantify the impact of driving forces on the variation in sediment load. It was found that a decrease in suspended sediment concentration accounted for approximately 100–125% of the basin-wide reduction in sediment load in the YZR basin. Construction of large reservoirs played a dominant role in sharp decline in sediment load across the basin, which was responsible for about 157 Mt yr−1 and 384 Mt yr−1 of sedimentation for the period 1969–2002 and 2003–2015, respectively. Soil conservation projects played the secondary role in reducing sediment load, which led to an average decrease of 234 Mt yr−1 in the entire basin during 1989–2015. Hence, more attention should be paid to changes in sediment load resulting from increasing human activities in the future. [ABSTRACT FROM AUTHOR]

The Jinsha River is the main source of sediment in the Yangtze River Basin. The variation of water discharge and sediment load not only affects the operation of the cascade reservoirs in the basin but also change the water and sediment conditions into the Three Gorges Reservoir. The Jinsha River Basin is divided into six regions based on the measured data of hydrological stations. Herein, the variation regularity and driving factors of water discharge and sediment load in the Jinsha River Basin are analyzed in the past 50 years using the Mann–Kendall and Rank Sum Test. Results show that the source of water and sediment in the Jinsha River Basin is different, and the abrupt and trend changes of water discharge and sediment load in different regions are evident different. Changes in precipitation, water and soil conservation projects, and the construction of reservoirs are the main driving factors of sediment load variation. The average annual sediment reduction load in the Jinsha River from 1998 to 2015 is approximately 99.57 × 106 t/y, of which the contributions of water discharge change and human activities to sediment load are 18.9% and 81.1%, respectively. The reduction of sediment load in the Jinsha River Basin can result in evident decrease in the sedimentation of cascade reservoirs, erosion of the downstream channel of the river, and considerable reduction of sediment load into the Three Gorges Reservoir. [ABSTRACT FROM AUTHOR]

The Gongshui River basin exhibits one of the most serious soil erosion areas in southern China, and has always been the key control area of national soil and water conservation programs. This study used daily precipitation, streamflow, and sediment concentration data collected from 1957 to 2015 from the main hydrological stations of the Gongshui River to investigate streamflow and sediment discharge variations and their responses to precipitation and human activities. The Mann-Kendall and Pettitt's test were used for trend and change-point detection. The double mass curve (DMC) method was employed to quantify the effects of precipitation change and human activities on hydrological regime shifts. The results showed insignificant trends of both annual precipitation and streamflow for all stations, while the sediment discharge of most stations exhibited significant decreasing trends. Change-point analyses revealed that all hydrologic stations except Mazhou had transition years. The estimation via DMC indicated that after the change point years, there was a rapid reduction in sediment discharge at Hanlinqiao, Fengkeng, Julongtan, Xiashan, and Chawu stations, but not at Mazhou, Ruijin, and Yangxinjian stations. Human activity provided a significantly greater contribution to sediment discharge than precipitation. The evidence clearly indicates that the degree and extension of conservation or destruction measures and the construction of large- and medium-sized reservoirs were the major factors significantly decreasing or increasing annual sediment discharge of the Gongshui River. This work could serve as the basis for decision making regarding river basin water resources management to estimate the effects of anthropogenic impacts on water and sediment discharge variations during the last few decades, thereby guiding adaptation and protection of the water resources of the Gongshui River flowing into the Poyang Lake. [ABSTRACT FROM AUTHOR]

In this study we analyze the scope and potential impact of reservoirconstruction on the world's river systems. Water storage behind the global population of large dams represents a 700% increase in the standing stock of natural river water, with residence times for individual impoundments spanning less than one day to several years. The imprint of such storage persists downstream. The mouths of several large rivers show a reservoir-induced aging of continental runoff that exceeds three months. Globally, the mean age of river water has likely tripled to well over one month. From both case studies and global synthesis, we find that this aging can lead to significant changes in net water balance, flow regime, reoxygenation of surface waters, and sediment transport. The pandemic construction of large reservoirs represents an important component of the terrestrial water cycle and one that merits due consideration in future global change studies. [ABSTRACT FROM AUTHOR]

The environmental effects, positive and negative, of reservoir creation and the dynamics of their construction in each continent and in certain countries are presented in this paper. The regional peculiarities of reservoir use are characterized ." [ABSTRACT FROM AUTHOR]